Abstract
Abstract Background Since the beginning of the COVID-19 pandemic, IBD patients have appeared to be less susceptible to a severe form of the disease, despite undergoing immunosuppressive treatments. Mannose binding lectin (MBL) is a humoral fluid-phase pattern recognition molecule (PRM) crucial for activating the lectin complement pathway. It is capable of binding to the spike protein and blocking SARS-CoV-2 infection. Low MBL expression has been linked to poor outcomes in both SARS and SARS- CoV-2 infections. In IBD patients, the role of MBL is controversial; low concentrations seem to predispose individuals to the development of IBD, while high concentrations have been observed in severe forms of Crohn's disease. Methods Since April 2020, 104 IBD patients have been enrolled, with 20% treated with mesalazine, 50% with Anti-TNFa, 20% with Vedolizumab, and 20% receiving no treatment. Additionally, 45 healthy controls (HC) from North Italy were included. Serum samples and colon biopsies from inflamed and non- inflamed mucosa were collected. Serum samples underwent an ELISA test to quantify circulating MBL concentration, and MBL gene expression in biopsies was analyzed using qPCR. Results Both Crohn's disease and Ulcerative Colitis patients exhibited significantly higher circulating MBL levels than HC (411.6 ± 45.5 ng/ml vs. 160.9 ± 35.3 ng/ml, p < 0.05). Patients treated with Anti-TNFa showed significantly higher circulating MBL levels compared to those not undergoing therapy (530.1 ± 76.5 ng/ml vs. 225.4 ± 61.6 ng/ml, p < 0.05) and patients receiving Vedolizumab (530.1 ± 76.5 ng/ml vs. 155.3 ± 32.1 ng/ml, p < 0.05). MBL intestinal gene expression is higher in IBD patients than HC (5.55 ± 0.9 vs. 2.36 ± 0.6; p=0.591) and tended to be elevated at similar levels in inflamed and non-inflamed mucosa (5.14 ± 1.4 vs. 5.79 ± 1.1; p=0.337), suggesting a prevalent genetic determination of MBL concentration regardless of the inflammatory background. Conclusion MBL appears to play a key role in SARS-CoV-2 infection. We demonstrate that IBD patients have, on average, higher circulating MBL levels than HC independently of their inflammatory status. The highest MBL levels were observed in patients treated with Anti-TNFa. These findings contribute to understanding the reported low mortality and hospitalization for COVID-19 among IBD patients treated with Anti-TNFa.
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